1.1: sulfuric acid; silica gel / dichloromethane / 120 h 2.1: sodium hydride / N,N-dimethyl-formamide; mineral oil / 0.25 h / 0 °C / Inert atmosphere 2.2: 0 - 20 °C / Inert atmosphere View Scheme

1.1: sulfuric acid; silica gel / dichloromethane / 120 h 2.1: trichlorophosphate / chlorobenzene / 6.5 h / 131 °C 2.2: 4 h / 110 °C 3.1: hydrogenchloride / 1,4-dioxane; water / 6 h / Reflux View Scheme

1: sulfuric acid; silica gel / dichloromethane / 120 h 2: trichlorophosphate / 1,1,2-trichloroethylene / 3.5 h / 87.5 °C View Scheme

sulfuric acid; silica gel in dichloromethane 120 h;